1. Field of the Invention
The present invention relates to an improved umbrella frame, which has an improved longitudinal supporting strength, and, in particular, has a lateral elastic property, so as to prevent the short ribs of the frame from breaking.
2. Description of Related Art
Normally, an umbrella of the related art is a light screen of silk, cotton, or other fabric, stretched on a folding frame with radiating ribs on a stick for holding above the head of a user as a protection against the rain or the sun. As shown in FIGS. 6 and 7, the frame of an umbrella having a stick (50) includes an upper sleeve (56) with a nest (57) set on the top end thereof, a mid runner(54), and a lower runner (51) being installed beneath the upper sleeve (56). A plurality of long ribs (58) are radiated around and pivotally connected with the nest (57). A plurality of U shaped metal-made short ribs (55) are radiated around the mid runner (54) and each of which are pivotally connected between the mid runner (54) and the long ribs (58). A plurality of stretchers (52) are radiated around the lower runner (51) and each of which are pivotally connected between the lower runner (51) and one of the short ribs (55). Thus, by pushing the lower runner (51) upwards, the stretchers (52) and the short ribs (55) are accordingly being pushed, and therefore, the short ribs (55) will be stretched outward along with the long ribs (58).
Structurally, the outward stretching of the long ribs (58) is supported by the short ribs (55) on an appropriate position of the long ribs (58), and the short ribs (55) are supported by the restoring force of a spring (53) which is installed between the lower runner (51) and the mid runner (54). However, the most breakage in the use of such an umbrella is the break of the U-shaped metal-made short ribs (55). Although the structure of the short ribs (55) is strong enough to support the stretched long ribs (58), its lateral strength is not as strong as the longitudinal strength such that it is easy to be deformed subject to the side impact.